Integrated circuits have become more “dense” over time, i.e., more logic features have been implemented in an IC of a given size. Part of this increase in density has led to development of a multigate device, such as a multiple gate field-effect transistor (“MuGFET”). A form of a MuGFET is a multiple independent gate field-effect transistor (“MIGFET”). Forms of MuGFETs may be planar or nonplanar. For example, a planar double-gate transistor and a Flexfet are planar forms of MuGFETs, and a FinFET and a Tri-gate or 3D transistor are nonplanar forms of MuGFETs. For purposes of clarity by way of example and not limitation, the following description is in terms of FinFETs, where FinFET generally refer to any fin-based, multigate transistor architecture without regard to the number of gates other than there are at least two gates.
Use of FinFET technology in an inductance-capacitance (“LC”) voltage controlled oscillator (“VCO”) presents a challenge for achieving a wide tuning range. Generally, this may be due to reliability and gate work function issues. Along those lines, a capacitance-voltage (“CV”) curve of a varactor, such as for example an NMOS varactor, may be shifted to higher voltages due to FinFET technology work function of such a varactor.
Hence, it is desirable and useful to provide a wideband NMOS LC VCO that overcomes one or more of these issues.